1. Technical Field
The present invention relates to improvements in light controlled optical switching devices.
2. The Prior Art
Research into optical switching devices, i.e., devices wherein light controls light, is one of the most intriguing research areas in modern laboratories. In this regard, there is a great deal of work underway in developing materials that will permit the construction of such devices. These materials are generally known as nonlinear optical materials. In particular, so-called "third-order nonlinear optical materials" are required for all-optical device constructions. Therefore, there exists a need to develop materials with enhanced third-order nonlinear optical susceptibilities for use in such optical switching devices.
Lanthanide bis-phthalocyanines have been known and studied for more than 25 years with most of the early research being focussed on their electrochemistry and their potential for use as electrochromic materials for display devices. Recent mass spectroscopy, magnetic susceptibility and ESR measurements indicating that these molecules are stable free radical systems, and demonstrations as to the intrinsic molecular semiconductor nature of the lanthanide bis-phthalocyanines, have generated renewed interest in the materials. Lutetium bis-phthalocyanine (Lu(Pc).sub.2) is the first reported molecular semiconductor and has been used to construct field-effect transistors.